Rf-coupled digital isolator

ABSTRACT

An RF-coupled digital isolator includes a first leadframe portion and a second leadframe portion, electrically isolated from one another. The first leadframe portion includes a first main body and a first finger. The second leadframe portion includes a second main body and a second finger. The first main body is connected to a first ground, and the second main body is connected to a second ground that is electrically isolated from the first ground. The first finger and the second finger are electrically isolated from one another, e.g., by a plastic molding compound that forms a package for the digital isolator. The first finger acts as a primary of a transformer, and the second finger acts as a secondary of a transformer, when an RF signal drives to the first finger. The first finger and the second finger can be substantially parallel or anti-parallel to one another.

This application claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application No. 60/928,856, filed May 11, 2007, and U.S.Provisional Patent Application No. 60/973,020, filed Sep. 17, 2007, eachof which are incorporated herein by reference.

FIELD OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to isolators, and morespecifically, to digital isolators that preferably operate at RFfrequencies.

2. Background

Isolation is important for various reasons. For example, isolation isimportant where common mode noise may be a problem. Isolation is alsoimportant where high-speed data transmission may be subject tointerference due to magnetic fields, and the like. Additionally,isolation is important where the ground of two devices are notcompatible. Further, isolation can be important to protect patients inmedical applications. These are just a few examples, which are not meantto be limiting.

Various devices have been developed for providing isolation. Forexample, an optical isolator (also known as an opto-isolator,optocoupler, photocoupler, or photoMOS) is a device that uses arelatively short optical transmission path to transfer a signal betweenelements of one or more circuit, typically a transmitter and a receiver,while keeping them electrically isolated. However, a disadvantage ofoptical isolators is that they can not typically operate at high speedsoften desired in digital communications. Additionally, since opticalisolators require an optical transmitting element and an opticaldetecting element, the size, cost and power consumption of such devicesis often greater than desired.

To overcome many of the deficiencies of optical isolators, digitalisolators have been developed. Some digital isolators are capacitivelycoupled. However, such devices are often larger than desired and/or arenot compatible with integrated circuit fabrication techniques. Otherdigital isolator devices combine high speed CMOS and air-core ormagnetic-core transformer technology to support high data speeds and lowpower. However, such transformers typically rely on windings that oftencause the size and cost of the transformers to be greater than desired.

SUMMARY

Embodiments of the present invention relate to RF-coupled digitalisolators, and methods for providing digital isolation. In accordancewith an embodiment of the present invention, an RF-coupled digitalisolator includes a first leadframe portion and a second leadframeportion, which are electrically isolated from one another. In accordancewith specific embodiments, the first and second leadframe portions areportions of a split leadframe. The first leadframe portion includes afirst main body and a first finger. The second leadframe portionincludes a second main body and a second finger. The first main body isconnected to a first ground, and the second main body is connected to asecond ground that is electrically isolated from the first ground.

In accordance with an embodiment, the first finger and the second fingerare electrically isolated from one another by a plastic molding compoundthat forms a package for the digital isolator. In accordance with anembodiment, the first finger acts as a primary of a transformer, and thesecond finger acts as a secondary of a transformer, when a radiofrequency (RF) signal drives to the first finger. In certainembodiments, the first finger and the second finger are substantiallyparallel to one another. In other embodiments, the first and secondfingers are substantially anti-parallel to one another. In someembodiments, the first finger and the second finger are eachsubstantially straight. In other embodiments, the first and secondfingers are curved, e.g., substantially spiral, yet still substantiallyparallel or anti-parallel to one another.

In accordance with some embodiments, a first die is mounted on the firstmain body, and a second die mounted on the second main body. A firstbondwire connects the first die to the first finger, and a secondbondwire connects the second die to the second finger. In accordancewith certain embodiments, the first die includes an oscillator thatgenerates the RF signal used to drive the first finger. The second diecan include an amplifier that amplifies a signal generated by the secondfinger when the RF signal drives the first finger. The first die canalso include a modulator, and the second die can also include ademodulator. The modulator within the first die can control theoscillator, based on one or more control signal provided to the firstdie. The demodulator can demodulate a signal output by the amplifier,and can provide a demodulated output signal to an output of the seconddie.

Further embodiments, and the features, aspects, and advantages of thepresent invention will become more apparent from the detaileddescription set forth below, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an RF-coupled digital isolator, according to anembodiment of the present invention.

FIG. 1B illustrates an RF-coupled digital isolator, according to anotherembodiment of the present invention.

FIG. 1C illustrates an RF-coupled digital isolator, according to afurther embodiment of the present invention.

FIG. 2 is a high level circuit diagram that illustrates some additionaldetails of the digital isolators of FIGS. 1A-1C, and which models someof the various elements of FIGS. 1A-1C as equivalent circuit components.

FIG. 3 is a high level circuit diagram that provides some additionaldetails to the diagram of FIG. 2, where simple binary modulation isused.

FIG. 4A illustrates an RF-coupled digital isolator, according to anembodiment of the present invention, which can provide for full-duplexcommunication.

FIG. 4B illustrates an RF-coupled digital isolator, according to anotherembodiment of the present invention, which can also provide forfull-duplex communication.

FIG. 5 illustrates an exemplary H-bridge circuit that can be implementedusing the digital isolators of the present invention.

DETAILED DESCRIPTION

FIG. 1A illustrates an RF-coupled digital isolator (often referred tohereafter simply as a digital isolator) 100, according to an embodimentof the present invention. The digital isolator 100 includes a splitleadframe 104, including a first leadframe portion 104 a and a secondleadframe portion 104 b. The leadframe portions 104 a and 104 b areencapsulated in an encapsulating material (e.g., plastic) to form apackage 102 for the digital isolator. Each leadframe portion 104 a and104 b can be made, for example, of a stamped or etched copper or steelalloy that is plated, but is not limited thereto.

Each leadframe portion 104 a and 104 b includes a corresponding mainbody 110 a and 110 b and a corresponding finger 120 a and 120 b. Thefingers 120 a and 120 b, which are isolated from one another by packagematerial (e.g., plastic molding compound), collectively provide atransformer, which may also be referred to as a “finger transformer”. Inthis embodiment, the finger 120 a acts as a primary of the transformer,and the finger 120 b acts as a secondary of the transformer, when aradio frequency (RF) signal drives to the finger 120 a.

Additionally, a die 130 a (also referred to as “die A”) is mounted onthe main body 110 a of the leadframe portion 104 a, and a die 130 b(also referred to as “die B”) is mounted on the main body 110 b of theleadframe portion 104 b. The die 130 a can include an integrated circuitthat provides transmission capabilities, and thus may also be referredto as a transmitter die. The die 130 b can include an integrated circuitthat provides receiving capabilities, and thus may also be referred toas a receiver die. It is also possible that each die 130 a and 130 b canprovide for both transmitting and receiving capabilities, and thus maybe transceiver dies. Such two way communications can be half-duplex.

The die 130 a also includes a plurality of pads, represented by smallsquares within the die 130 a. The pads of the die 130 a are connected tocomponents outside the die 130 a via bond wires, represented by boldlines. One of the pads of the die 130 a is connected to the finger 120 aby a bond wire 132 a. Another of the pads of the die 130 a is connectedvia a ground bond wire to the main body 110 a, which in turn isconnected to a ground (i.e., Gnd_A) via another bond wire. A further padof the die 130 a receives an input signal. Still another pad of the die130 a receives a voltage (Vs_A) used to power the die 130 a.

Similarly, the die 130 b includes a plurality of pads, represented bysmall squares within the die 130 b, which are connected to componentsoutside the die 130 b via bond wires, represented by bold lines. One ofthe pads of the die 130 b is connected to the finger 120 b by a bondwire 132 b. Another of the pads of the die 130 b is connected via aground bond wire to the main body 110 b, which in turn is connected to aground (i.e., Gnd_B) via another bond wire. Gnd_A and Gnd_B areelectrically isolated from one another. A further pad of the die 130 bprovides an output signal. Still another pad of the die 130 b receives avoltage (Vs_B) used to power the die 130 b. Where the dies 130 a and 130b can function as transceivers, the same pad on each die can bothreceive an input, and provide an output, or separate pads can beprovided for each function.

In FIG. 1A, the fingers 120 a and 120 b are shown as being parallel toone another. In an alternative embodiment, shown in FIG. 1B, anRF-coupled digital isolator 100′ includes fingers 120 a and 120 b thatare anti-parallel to one another, which causes them to be anti-phase(i.e., 180 degrees out of phase). There is a parasitic capacitivecoupling between the fingers 120 a and 120 b when the fingers areparallel to one another, as well as when the fingers are anti-parallelto one another. However, a benefit of the fingers being anti-parallel toone another is that the parasitic capacitive coupling in theanti-parallel configuration increases signal transfer, due to the phraserelationships between the magnetic and coupling modes. In contrast, theparasitic capacitive coupling in the parallel configuration will reducesignal transfer.

In FIGS. 1A and 1B the fingers 120 a and 120 b are shown as beingsubstantially straight, however that need not be the case, as can beappreciated from FIG. 1C. More specifically, FIG. 1C shows an embodimentof an RF-coupled digital isolator 100″ where the fingers 120 a and 120 bare anti-parallel, but the fingers 120 a and 120 b are spiraling, whichhas the affect of increasing their mutual coupling inductance (and thus,increasing their coefficient of coupling). The fingers 120 a and 120 bin FIG. 1C can alternatively be parallel to one another. Similar orcommon reference numbers in the figures, including FIGS. 1A-1C, are usedto reference similar components or elements.

The distance between the fingers 120 a and 120 b, the shape of thefingers 120 a and 120 b, and the length of the fingers 120 a and 120 b,affects the parasitic capacitance (C_(parasitic)) between the fingersand the coefficient of coupling (K). An exemplary distance between thefingers 120 a and 120 b is 10 milli-inches, but other distances are alsowithin the scope of the present invention.

As will now be described with reference to FIG. 2, the die A (130 a)forces a current preferably in the GHz range into the finger 120 a,which returns into the leadframe main body 110 a and back into die A'sground bond wire. The fingers 120 a and 120 b, which as mentioned aboveare isolated from one another, have a magnetic coupling and a mutualinductance. The parasitic capacitance is illustrated in FIG. 2 by thedashed line capacitor labeled C_(parasitic). The coefficient of couplingis illustrated by the “K” in FIG. 2, indicating that there is acoefficient of coupling between the two fingers 120 a and 120 b (statedanother way, there is a mutual inductance between the two fingers 120 aand 120 b). The transfer advantageously increases with frequency.Accordingly, high operating frequencies are desired. The operatingfrequencies are preferably outside the frequency spectrums assigned tocell phones and Bluetooth devices. More specifically, it is desired thatthe operating frequency of the digital couplers of the present inventionare greater than or less than 2.4 GHz. In specific embodiments, theoperating frequency is nominally ˜3 GHz.

Referring to the circuit diagram of FIG. 2, some additional details ofthe dies 130 a and 130 b are provided and various bond wires are shownas inductors, due to their inductive qualities. Additionally, in FIG. 2,each of the fingers 120 a and 120 b is also shown as an inductor, alsodue to their inductive qualities. The die 130 a is also shown asincluding an oscillator 220 and a modulator 210. In accordance withspecific embodiments, the oscillator 220 produces an oscillating signalof ˜3 GHz and ˜3 milliamp peak-to-peak (mApp), although signals of loweror higher frequencies and/or lower or higher amplitudes are alsopossible and within the scope of the present invention. The modulator210 receives one or more input signal lines, which instruct themodulator 210 how to control the oscillator 220. Where simple binarymodulation (also known as “on/off modulation”) is used, the modulator210 can be as simple as a buffer, as shown at 310 in FIG. 3. Any othermodulation technique that is known, or developed in the future, canalternatively be used, including, but not limited to, amplitudemodulation, quadrature modulation, etc.

Returning to the circuit diagram of FIG. 2, the die 130 b is shown asincluding an RF amplifier 230 and a demodulator 240. The RF amplifier230 amplifies the signal received by the finger 120 b, and provides theamplified signal to the demodulator 240. The type of demodulator usedshould correspond to the type of modulation provided by the modulator210. For example, where simple binary modulation is used, thedemodulator 240 can include a rectifier 330 followed by a comparator340, as shown in FIG. 3. FIG. 3 also illustrates that the rectifier 330can include a diode D1 and a capacitor C_(R), but is not limitedthereto.

Returning again to FIG. 2, each of the dies 130 a and 130 b optionallyalso includes a tuning capacitor, labeled C_(A) and C_(B), used to tunethe resonance of the circuit of each die. The parasitic capacitance(C_(parasitic)), mutual inductance (M), and coefficient of coupling (K)between the fingers 120 a and 120 b also affect the resonance.Accordingly, the dimensions of the fingers 120 a and 120 b, distancetherebetween, and components of the circuits of each die 130 a and 130 b(including the values of tuning capacitors C_(A) and C_(B)) can beselected to provide a desired resonance.

Still referring to FIG. 2, a logic input signal provided to die A (130a) causes the oscillator 220 to oscillate and provide an RF signal tothe finger transformer. More specifically, an oscillating signal isprovided from the oscillator 220, via the bond wire 132 a, to the finger120 a. The oscillating current (and/or voltage) provided to the finger120 a causes an oscillating current (and/or voltage) at the secondfinger 120 b, which is amplified by the amplifier 230. The output of theamplifier 230 is demodulated by the demodulator 240.

In accordance with specific embodiments of the present invention,presuming a 3 GHz oscillation frequency, and ˜3 mApp drive signal fromdie A (130 a), the output of the finger transformer can recover ˜45millivolts peak-to-peak (mVpp). Presuming a Q of ˜3 at each die 130 aand 130 b, ˜400 mVpp can be recovered when resonating with capacitorsC_(A) and C_(B).

As mentioned above, the circuit shown in FIG. 2 can be used for one waytransmission of a signal, e.g., from die A to die B, or for two wayhalf-duplex communication. To provide for two way half-duplexcommunication, die A can also include an RF-amp and a demodulator, anddie B can also include an oscillator and a modulator. Alternatively, adie similar to die B can also be mounted on the main body 110 a of theleadframe portion 104 a, and a die similar to die A can also be mountedon the main body 110 b of the leadframe portion 104 b. In other words,each lead frame portion 110 a and 110 b can include a die fortransmitting signals and a separate die for receiving signals, or acommon die can be for both transmitting and receiving signals.

Each leadframe portion 104 a and 104 b need only include one finger,where half-duplex communication is used. For example, referring to FIGS.1A-1C, the finger 120 a can be used for transmitting signals, as well asreceiving signals, so long as the transmitting and receiving areoccurring at different times, as is the case in half-duplexcommunication.

Alternatively, each of the leadframe portions 104 a and 104 b can havean additional finger, as shown in FIGS. 4A and 4B. Referring to FIGS. 4Aand 4B, the leadframe portion 104 a is shown as also having a finger 420a, and the leadframe portion 104 b is shown as also having a finger 420b. The additional fingers 420 a and 420 b, which are isolated from oneanother by package material (e.g., plastic molding compound)collectively provide a second transformer, which may also be referred toas a second “finger transformer”. FIGS. 4A and 4B differ from oneanother, in that in FIG. 4A each pair of fingers that form a fingertransformer are parallel to one another, where in FIG. 4B each pair offingers that form a finger transformer are anti-parallel to one another.While the fingers in FIGS. 4A and 4B are shown as being substantiallystraight, that need not be the case, as can be appreciated from FIG. 1Cdiscussed above. In the embodiments of FIGS. 4A and 4B, when the fingers120 a and 420 b are driven by RF signals, the fingers 120 a and 120 bact, respectively, as the primary and secondary of the first fingertransformer, and the fingers 420 b and 420 a act, respectively, as theprimary and secondary of the second finger transformer.

Referring to the digital isolators 400 and 400′ of FIGS. 4A and 4B, thefinger 120 a can be dedicated to transmitting signals and the finger 420a can be dedicated to receiving signals, or vice versa. Similarly, thefinger 120 b can be dedicated to receiving signals, and the finger 420 bcan be dedicated to transmitting signals, or vice versa. In this manner,full duplex communication can be provided.

FIGS. 4A and 4B also show two dies 130 a and 430 a mounted on theleadframe portion 104 a, and two dies 130 b and 430 b mounted on theleadframe portion 104 b. One die on each leadframe portion can be usedfor produce signals used to drive a finger for transmission (e.g.,including performing modulation), and the other die on the leadframeportion can be used, e.g., for amplifying and demodulating receivedsignals. Alternatively, the dies shown on each leadframe portion can becombined so that each leadframe portion has mounted thereon a single dieused for both receiving and transmitting functions. It is also withinthe scope of the present invention to add one or more additionalfinger(s) to each leadframe portion. Also, it is possible to add one ormore additional leadframe portion(s), i.e., use more than two leadframeportions, so that more isolation regions exist. For example, eachleadframe portion shown in FIGS. 4A and 4B can be separated into twoleadframe portions, resulting in four separate leadframe portions, eachhaving a finger. Further, it is also noted that leadframe portions neednot be symmetrical to one another, i.e., non-symmetrical layouts canalso be used.

In certain embodiments, the digital isolator can be formed in a ceramicpackage, such as but not limited to a hermetic ceramic package. Such aceramic package can include a lead frame embedded in a paste layerbetween ceramic top and bottom covers. In other words, the leadframeportions 104 a and 104 b that include a corresponding finger 120 andmain body 110 can be embedded between ceramic layers. The dies (e.g.,130 a and 130 b) can be connected to a ceramic layer, which may or maynot be the same layer on which the fingers 120 are formed. In suchembodiments, air or some other gas can provide electrical isolationbetween a pair of fingers. It's also possible that the main bodies(e.g., 110 a and 110 b) and fingers (e.g., 120 a and 120 b) be formeddirectly on a ceramic layer using any of a variety of techniques, suchas, but not limited to, chemical vapor deposition, sputtering, etching,photolithography, masking, etc. The dies (e.g., 130 a and 130 b) can beconnected to such a layer, which may or may not be the same layer onwhich the fingers 120 are formed. Again, air or some other gas canprovide electrical isolation between a pair of fingers. In still otherembodiments, the digital isolator can be formed as a hybrid integratedcircuit. For example, the main bodies (e.g., 110 a and 110 b) andfingers (e.g., 120 a and 120 b) can be formed on a printed circuitboard, to which are attached the dies (e.g., 130 a and 130 b). In suchembodiments, molding compound can provide electrical isolation andmechanical support between fingers. In the alternative embodiments justexplained above, conductive traces and/or vias can be used in place ofbond wires to connect dies to fingers, or bond wires can still be used.

An advantage of certain embodiments of the present invention is that adigital isolator can be provided by producing a transformer using asplit leadframe and plastic molding compound that are available intypically chip assembly processes. An advantage of certain embodimentsof the present invention is that no windings are necessary to provide atransformer for a digital isolator, likely reducing the size and cost ofa resulting digital isolator. Another advantage of certain embodimentsof the present invention is that the designs discussed above work wellat high frequencies above cell phone and Bluetooth spectrums, and suchembodiments, if tuned appropriately, can also inherently rejectfrequencies in the cell phone and Bluetooth spectrums.

The RF-coupled digital isolators of the present invention can be usedfor numerous different applications. For example, the RF-coupled digitalisolators can be used in a power H-bridge, e.g., in power supplies ormotor controllers, e.g., as shown in FIG. 5. Other implementation of anH-bridge are also possible, and within the scope of the presentinvention.

Additionally, the RF-coupled digital isolators can be used tocommunicate with switching power transistors and power lines. Further,the RF-coupled digital isolators of the present invention can be usedfor long distance communications (e.g., RS485). The RF-coupled digitalisolators of the present invention can be especially useful for powerswitching of 50 W or greater. The RF-coupled digital isolators of thepresent invention can also be used to reduce dead time for DC to DCconverters, e.g., to 10 nsec. These are just a few applications for thedigital isolators of the present invention, which are not meant to belimiting.

The forgoing description is of the preferred embodiments of the presentinvention. These embodiments have been provided for the purposes ofillustration and description, but are not intended to be exhaustive orto limit the invention to the precise forms disclosed. Manymodifications and variations will be apparent to a practitioner skilledin the art. Embodiments were chosen and described in order to bestdescribe the principles of the invention and its practical application,thereby enabling others skilled in the art to understand the invention.It is intended that the scope of the invention be defined by thefollowing claims and their equivalents.

1. An RF-coupled digital isolator, comprising: a first leadframe portionincluding a first main body and a first finger; a second leadframeportion including a second main body and a second finger, the secondleadframe portion electrically isolated from the first leadframeportion; the first main body connected to a first ground; the secondmain body connected to a second ground that is electrically isolatedfrom the first ground; a first die mounted on the first main body; and asecond die mounted on the second main body; wherein the first finger andthe second finger are electrically isolated from one another; andwherein the first finger acts as a primary of a transformer, and thesecond finger acts as a secondary of a transformer, when an RF signaldrives to the first finger.
 2. The RF-coupled digital isolator of 1,wherein the first finger and the second finger are electrically isolatedfrom one another by a molding compound that forms a package for thedigital isolator.
 3. The RF-coupled digital isolator of claim 1, furthercomprising: a first bondwire that connects the first die to the firstfinger; and a second bondwire that connects the second die to the secondfinger.
 4. The RF-coupled digital isolator of claim 1, wherein the firstand second leadframe portions are portions of a split leadframe.
 5. TheRF-coupled digital isolator of claim 1, wherein the first finger and thesecond finger are substantially parallel to one another.
 6. TheRF-coupled digital isolator of claim 5, wherein the first finger and thesecond finger are each substantially straight.
 7. The RF-coupled digitalisolator of claim 5, wherein the first finger and the second finger areeach curved.
 8. The RF-coupled digital isolator of claim 7, wherein thefirst finger and the second finger are substantially spiral.
 9. TheRF-coupled digital isolator of claim 1, wherein the first finger and thesecond finger are substantially anti-parallel to one another.
 10. TheRF-coupled digital isolator of claim 9, wherein the first finger and thesecond finger are each substantially straight.
 11. The RF-coupleddigital isolator of claim 9, wherein the first finger and the secondfinger are each curved.
 12. The RF-coupled digital isolator of claim 11,wherein the first finger and the second finger are substantially spiral.13. The RF-coupled digital isolator of claim 1, further comprising: anoscillator, within the first die, that generates the RF signal; a firstbondwire that connects the first die to the first finger, and providesthe RF signal from the first die to the first finger; a second bondwirethat connects the second finger to the second die; and an amplifierwithin the second die that amplifies a signal generated by the secondfinger when the RF signal drives the first finger.
 14. The RF-coupleddigital isolator of claim 13, further comprising: a modulator within thefirst die; and a demodulator within the second die; wherein themodulator controls the oscillator, based on one or more control signalprovided to the first die; and wherein the demodulator demodulates asignal output by the amplifier and provides a demodulated output signalto an output of the second die.
 15. An RF-coupled digital isolator,comprising: a split leadframe including a first leadframe portion and asecond leadframe portion that are electrically isolated from oneanother; the first leadframe portion including a first finger; and thesecond leadframe portion including a second finger; wherein the firstand second fingers have a mutual inductance that enable a change involtage and/or current in one said finger to be detected by the othersaid finger.
 16. The RF-coupled digital isolator of claim 15, wherein:the first leadframe portion includes a first main body from which thefirst finger extends; the second leadframe portion includes a secondmain body from which the second finger extends; and when one of saidfingers is driven by an RF signal, the said finger that is driven actsas a primary of a transformer, and the other said finger acts as asecondary of a transformer.
 17. The RF-coupled digital isolator of claim16, further comprising: a first die mounted on the first main body; asecond die mounted on the second main body; a first bondwire thatconnects the first die to the first finger; a second bondwire thatconnects the second die to the second finger; and a plastic moldingcompound between the first and second fingers, to provide the electricalisolation between the fingers.
 18. The RF-coupled digital isolator ofclaim 17, wherein: the first main body is connected to a first ground;and the second main body is connected to a second ground that iselectrically isolated from the first ground.
 19. A method for providingdigital isolation, comprising: driving a first finger of a firstleadframe with an RF signal; and detecting a signal at a second fingerof a second leadframe, as a result of the first finger being driven bythe RF signal and the mutual inductance between the first and secondfingers, wherein the first and second fingers are electrically isolatedfrom one another.
 20. The method of claim 20, further comprising:receiving an input signal; performing modulation, based on the inputsignal, to produce the RF signal that drives the first finger; anddemodulating the signal detected at the second finger, or an amplifiedversion thereof, to produce an output signal.
 21. A system, comprising:a first portion of a circuit; a second portion of the circuit; and adigital isolator between the first and second portions of the circuit;wherein the digital isolator includes a first leadframe portionincluding a first main body and a first finger; a second leadframeportion including a second main body and a second finger, the secondleadframe portion electrically isolated from the first leadframeportion; the first main body connected to a first ground; the secondmain body connected to a second ground that is electrically isolatedfrom the first ground; a first die mounted on the first main body; and asecond die mounted on the second main body; wherein the first finger andthe second finger are electrically isolated from one another; andwherein the first finger acts as a primary of a transformer, and thesecond finger acts as a secondary of a transformer, when an RF signaldrives to the first finger.